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Jan Kwiecinski 1938 - 2003…absolutely the kindest man I have ever met in my whole life. …. CERN Courier, Jan-Feb 2004
Some of Jan’s proteges:
Krzysztof Golec-Biernat excellent jointLeszek Motyka paper onAnna Stasto saturation in BFKL
Michal Praszalowicz BKP eq. for the odderon
Problem is low energy QCD 3 examples from W/S
Muon g-2Teubner
Pentaquarks
Several expts see an exotic B=1, S=1baryon resonance in K+n or K0p channels(1530) with narrow width <10 MeV
KarlinerKarliner
HERMES
but is s(1530)seen by H1 ??
but H1 see c
which is not seen by ZEUS ?
The chiral soliton (Skyrme) model (SM) predicted s(1530)with <15 MeV, JP=(1/2)+ in a 10 of SU(3)f
Praszalowicz(1987), Diakonov,Petrov,Polyakov(1997)
s(1530)
N
NA49 see--(1860)which is not seenby ZEUS & WA89
s(1530) uudds
N
Postdictive interpretation in terms of constit.quark model (CQM)s = uudds in P-wave (1/2)+ in 10Karliner & Lipkin (ud) (uds) predict c(2985 +/- 50 MeV))Jaffe & Wilczek (ud) (ud) s predict c(2710 MeV) H1 see c(3099 MeV)Anticipate (c)~10(s) from KN to DN phase space
SM & CQM are complementary:~shell & droplet nuclear models
(1860)
Karliner & Lipkin expectM() - M(s) < 300MeV,whereas expt ~330MeV uuddd, uudss
uussd
~ms/3
Third example of expt. led QCD:
Wu-Ki Tung’s “trip down memory lane”
He showed us some the twists & turns of thePDF input needed to keep pace with the new experimental measurements
DIS Bjorken scaling quarks (of spectroscopy) really exist Gross & Wilczek, Politzer colour SU(3) gauge theory (QCD) logarithmic scaling violations
A famous experimentalist to Wilczek:
You expect us to measure logarithms !Not in your lifetime young man !
Fixed target DIS ep, ed, N; D-Yan, W asym, Tevatron jetsHERA epglobal DGLAP parton analyses CTEQ, MRSTanalyses to selected data sets Botje, Alekhin, ZEUS, H1…
Expect small x processesto be driven by the gluon.
Surprise at v.low scales appear to be dominated byby singlet sea quarks valence-like or -ve gluon !
Sea quarks & gluons not(perturbatively) connected.
x
Remarkably consistent, considering v.differentselection of data fitted –but then all include the crucial BCDMS data
s from DIS
DIS 1993
(Lum=20 nb-1)
Now
Reg
ge
conf
inem
ent
BF
KL
DGLAP
ln Q2
ln 1/x
saturatio
n
absorptive corr.
HERA
HERA has opened up the small x domain
• how large is the DGLAP domain ?
• are BFKL (log 1/x) effects evident ?
• is there any evidence of absorptive corrections, or even parton saturation ?
• HERA observes diffractive DIS (at ~10% of DIS). What role does it play ?
• what would we like HERA to measure now ?
CTEQ gluon
compared to
MRST error band
Q2=5
Q2=100
Parton uncertainties due to stat/sym errors of data fitted
Other uncertainties includeselection of data fitted; choice of x,Q2,W2 cutsTheoretical uncertaintieshigher-order DGLAP NLO, NNLO…Moch,Vermaseren,Vogtsln(1/x) and sln(1-x) effects absorptive corrections from parton recombinationresidual higher-twist effectsQED effectsUncertainties due to input assumptionsisospin-violating effects MRSTs not equal to s CTEQheavy-target correctionschoice of input parametrization Thorne, Tung
no NuTeV sin2 anomaly
MRST find tension between data sets --- F2 data (x~0.01) and Tevatron jets (x~0.07-0.5) both prefer more gluon
NNLO more stable to the x=0.005 cut.
tension removedif only x>0.005data fitted
CTEQ havestability to cuts.Difference may be due to MRST input formwith explicit negativegluon term ??
Experimental ways to determine the gluon
• FL most direct x ~ 10-4 - 10-3
• Prompt photon data (WA70,E706) and theory problems
• Tevatron jets x ~ 0.07 – 0.5
• HERA jets x ~ 0.01 - 0.1 Cooper-Sarkar, Butterworth (ZEUS)
• Diffractive J/ at HERA g2 x ~ 10-3 need to improve theory first attempt by Szymanowski
(+ momentum sum rule)
Simulation of FL by Klein
Extremely valuable if HERA could measure FL with sufficient precision --- to pindown the low x gluon
FL
Thorne
Q2=10
Q2=5
Q2=20 Q2=40Data are Klein’ssimulation
F2
Lower HERA beam energies could also provide a valuablecheck on the large x data, which rely on BCDMS. Also ed?
F2
DGLAP
ln 1/x resum ?abs. corr. ?
Higgs
Salam
Diffractive DIS data
mq=0
mq=140 MeV
Original Golec-Biernat, Wusthoff fit
Include charm.
Relate to xg &evolve in Q2
+Bartels,Kowalski
Is it saturation orconfinement ?
There are other dipole fits withoutsaturatione.g. Forshaw,Kerley & Shaw.
Saturation
No definitive experimental evidence
Much theoretical activity and progress-----BK, JIMWLK, KPP…equations
A glimpse for pedestrians (with help from Icanu, Golec-Biernat)
Complementary approaches
p rest frame / fast dipole fast p / slow dipole
bare dipole
evolved pwave fn.(cgc)
wave fn.
Balitsky Kovchegov eq.
Jalilan Marian, Iancu, McLerran,Weigert, Leonidov, Kovner eq.
leads to
Munier & Peschanski: The BK eq. is approximatedby the Kozmogorov,Petrovski,Pisconov eq., which is well studiedin condensed matter physics
Diffractive DIS data
ln Q2
highertwist
Bartels,Ellis,Kowalski & Wusthoffbase parametrizationon these forms
rapidity gap survival factor S2 ~ 0.1
HERA
S2 ~ 1
*
Survival factors calc. from2-ch eikonal model basedon multi-Pom. exchange &s channel unitarity KKMR
Diffractive photoproduction of dijets: direct compt. S2 ~ 1 resolved compt. (hadron-like) S2 ~ 0.34
NLO analysis byKlasen & Kramer,--good agreementwith prelim. H1 data
Note in LO analysis,data would prefer S2 ~ 1 for resolved
Exclusive diffractive Higgs signal pp p+H+p
Higgs
For a 120 GeV (SM) Higgsat the LHC (L=30 fb-1)11 events / 4 backgroundFor MSSM with tan~50, mA~130 GeV70 events / 3 background
Advantages: 2 indep. MH det.1. missing mass to proton taggers (M~1 GeV)2. bb decay (M~10 GeV)
bb backgd v.suppressed by Jz=0 selection rule
S2 = 0.026
Khoze,Martin,Ryskin
Health warning:Royon confirms KMRprediction for cross section,but notes present technologywill yield smaller S/B
DIS continues to flourish – the W/S contains more results & research activity than those on any other topic
Much remains to be learnt – we are just getting to gripswith many basic problems – data are not sufficient / absent !
It is inconceivable that HERA will not measure FL withsufficient precision to determine the gluon – low energyruns must be done – they will also determine large x PDFsESSENTIAL FOR THE LHC
bb in DIS & photoproduction, electron runs for CC & xF3,
precision on F2(diffractive),…
exotica
There are so many crucial measurements still tobe done, and unless the correct action is set intomotion soon, time will run out for HERA (& DIS)while the physics potential of the machine is stillcoming to its prime.
A global analysis is required – can the eRHICenthusiasts be persuaded to join in the push fora future HERA programme – scientifically it wouldseem to be a far better solution all round.